Apparatus for converting thermal energy to mechanical energy



June 5, 1962 c. E. HAJNY 3,038,103

APPARATUS FOR CONVERTING THERMAL ENERGY TO MECHANICAL ENERGY Filed April 8, 1957 lvrll Y Hull INVENTOR. Charles E. Hajny Arr' s 3,038,108 APPARATUS FOR CQNVERTING THERMAL ENERGY T MECHANICAL ENERGY Charles E. Hainy, Milwaukee, Wis, assignor, by mesne assignments, to Minnesota Mining and Manufacturing Company, St. Paul, Minn, a corporation of Delaware Filed Apr. 8, 1957, Ser. No. 651,430 Claims. (Cl. 318-429) This invention relates in general to motors, and more particularly to motors characterized by step-'by-step operation.

It is a general object of this invention to provide an improved step-by-step motor including electromagnetic operator means and energizing means for intermittently energizing said operator means in a novel manner not requiring the use of circuit-interrupting contacts.

lt is a further object of this invention to provide an improved motor as aforementioned which, by Virtue of the incorporation therein of a heat sensitive energizing means, is well adapted for use in connection with fluid fuel burning apparatus, for example with heat sensitive energizing means, in coacting relation with a pilot burner, the heat of burning fuel at said pilot burner affording, by itself, sufficient energy for operation of said motor. Thus, advantage can be taken of the fact that operation of said motor is dependent upon the burning of fuel at said pilot burner, for example, in the control of fuel flow to said apparatus by control means actuated by said motor.

It is a more specific object of this invention to provide a step-by-step motor as above set forth wherein the electromagnetic operator means is intermittently energized in response to oscillatory movement of heat sensitive means in the form of a thermoelectric generator which moves into and out of heating relation with a source of heat.

A further specific object of this invention is to provide an improved motor of the aforementioned character having an adjustable resistance means for varying the frequency of the intermittent energization of the electromagnetic operator means and thereby the speed of said motor.

It is a further object of this invention to provide an improved motor of the class described which is ruggedly practical for field use, does not require hermetic scaling, is relatively easy to manufacture by mass production techniques, and is otherwise well-adapted for the purposes for which it was designed.

A further object of this invention is to provide a device of the aforenoted characteristic which is compact, has relatively few moving parts, is easily installed by non-skilled technicians, and readily adapted for multiplicity of uses with fluid fuel burning apparatus and other equipment.

The novel features which are characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation together with additional objects and advantages thereof will best be understood by the following description of a specific embodiment when read in connection with the accompanying drawings, in which:

FIGURE 1 is a front view of a motor embodying the inventive concept, portions being shown in section and other portions being shown semi-diagrammatically;

FIGURE 2 is a plan view taken along the line 2--2 of FIGURE 1; and

FIGURE 3 is a left-hand end view of the structure depicted in FIGURE 1.

' Essentially the improved motor includes an oscillating I 3,938,168 Patented June 5, 1962 pivotal lever having electromagnetic operator means at one end and thermoresponsive energizing means for Said operator at the other end. The principle of operation is that energization of the electromagnetic operator means causes movement of the heat responsive energizing means from a first to a second position, i.e., for example, into and out of heat transfer relation with respect to a source of heat, and when, for example, interrupting the heating of said energizing means to, in turn, deenergize the electromagnetic operator means, whereupon said lever and energizing means are returned to the heating position by suitable biasing means to complete a cycle of operation. Ratchet means is associated with the pivotal lever to afford step-by-step actuation of a driven member in response to cycling of said operator and lever.

More particularly, the improved motor, which is indicated generally by the reference numeral 10, comprises a base or supporting plate 11 having fixed thereon, a generally U-shaped bearing member 12. The bearing member 12 is formed with a pair of upstanding spaced arms 13 and 14, arm 13 having a lug 15 extending to the right as shown in FIGURE 1 for purposes hereinafter appearing. The spaced arms 13 and 14 are formed with suitable bearing bores 13b and 1411 respectively for receiving a shaft 16 which is mounted for turning movement therein. As shown in FIGURE 2, one end of shaft 16 has a driven member such as a suitable toothed gear 17 fixed thereon to afford a driving connection with, for example, the gear train of a timing device, energy storing means, or with other devices, particularly those wherein a constant speed driving mechanism is suitable or desired.

Means affording step-by-step rotation of shaft 16 and gear 17 is provided by ratchet means 33, electromagnetic operator means 34, energizing means 35 for the operator means said energizing means also including heat source means 36. Means for mechanically connecting the energizing means 35, operator means 34 and ratchet means 33 may be provided by an elongated lever 18 which is pivot-ally and loosely mounted on shaft 16 intermediate the upright supporting arms 13 and 14. The lever 18 is biased in a clockwise direction by a suitable spiral spring 27 one end of which is anchored to a lug 13a on support member 13 and the other end of which is anchored to a lug 18:: on lever 18.

As perhaps best shown in FIGURE 1, the right-hand end of lever 18 mounts an electromagnet forming part of operator means 34 and comprising a generally U-shaped magnet core 19 fixed on said lever for movement therewith. The magnet core 19 is formed with upstanding spaced arms 20 and 21 having a suitable energizing winding 23 thereon. The operator means 34 further comprises an armature 26 which may be fixedly mounted on a suitable non-magnetic bracket 45 carried by base member 11 and cooperable with the pole faces of magnet core 19.

The energizing means 35 for the operator means 34 includes portion mounted on the other or left-hand end of lever 18, which portion may comprise thermoelectric generator means 22 and cooperable with and relatively movable with respect to a suitable heat source indicated generally at 36. The generator means 22 may partake of the form shown and described in the copending application of Robert W. Fritts, Serial No. 641,540 filed February 21, 1957, now Patent No. 2,961,474 and assigned to the assignee of the present application. The generator disclosed in application Serial No. 641,540 takes the form of a thermocouple having embodied therein a thermoelement of semi-metallic material having high thermoelectric power and relatively low thermal conductivity. Rapid response of said generator to changes in the temperature to which the hot junction thereof is subjected is afiorded by structural features including relatively short length of the semi-metallic thermoelement, small thermal capacity structure at the hot junction, and large thermal capacity structure at the cold junction. For purposes of understanding the present invention, sui'lice it to say that the thermoelectric generator 22 may be of any suitable type that delivers a predetermined upon exposure of a hot junction area of heat sensing portion 22a thereof to heat, for example, by contact with a heated member such as the member 28 to be described, and which will rapidly cool and drop its EMF. output level below a predetermined level upon relative movement to spaced relation with respect to said heated member. The thermoelectric generator 22 is connected to energize electromagnet winding 23 through a suitable conductor 24, one terminal of said generator and one terminal of said winding being grounded to the lever arm 18 as shown, and the other terminals thereof being connected by said conductor. The flux generated by energized winding 23 is operable (under certain conditions to be explained) to cause the movement of the electromagnet core 19 toward the armature 26 and counterclockwise movement of the lever 18. This lever movement separates generator 22 from heated member 28, whereupon the generator cools and the level of the produced thereby drops.

The heat source means 36 is here shown comprising a pilot burner 40 which is fixedly mounted on a suitable lug 25, projecting from an upstanding bracket member 46 mounted on base 11. The pilot burner, when ignited, produces a flame 29 which is adapted to impinge upon one portion 28a of a Z-shaped metallic heat conducting member 28 insulatably mounted on bracket 46, as through heat insulating member 47 fixed, as by rivets 48, to said bracket and member. Heating of portion 23a of member 28 causes said member to become heated throughout its entire extent. It will be noted that when the oscillating lever 18 is in the position shown in FIGURE 1, the hot junction area 22a of thermoelectric generator 22 is positioned in contact with a portion 28b of metallic Z- shaped heat conductor 28.

Step-by-step ratchet means is provided to drive the shaft 16 and gear 17, upon oscillation of lever arm 18. A ratchet wheel 30 is fixedly or drivingly mounted on shaft 16 and is engaged by two spring loaded pawls 31 and 32, pawl 31 being carried by lever 18 to advance ratchet wheel 30 in a counterclockwise direction one notch upon every oscillation of said lever. Spring loaded pawl 32 is suitably mounted on a lug formed on bearing member 12 and prevents clockwise movement of wheel 30, for example, during clockwise movement of lever 18.

The operation of the device is as follows: Assume the following initial conditions: Pilot burner 40 ignited and producing flame 29 which is heating Z-shaped heat conducting member 28 at 28a, the heat being transferred by conduction to portion 28b. The hot junction area 22a of the thermoelectric generator 22 is biased into contact with heated portion 28b by spring 27 which simultaneously biases the electromagnet core 19 away from the armature 26, all as is shown in FIGURE 1 of the drawing.

The thermoelectric generator 22, since it is in contact with heat conductor 28b, generates an which energizes winding 23 of the electromagnet 19. When generator 22 is heated to a predetermined level, a magnetic flux is developed by winding 23, which flux aifords an attractive force greater than the opposing force of spring 27 causing attractive movement of the magnet 19 toward engagement with armature 26 and pivoting of the lever 18 in a counterclockwise direction. This counterclockwise movement of lever arm 18 causes pawl 31 to advance ratchet wheel 30 one step in a counterclockwise direction and simultaneously causes disengagement of thermoelectric generator 22 from the heat conductor 28. This moves the generator from a heating or heat sensing position to a cooling or non-sensing position. The armature and magnet remain in coupled relation until the generator cools to a point where the developed thereby falls below that required to retain the armature and magnet in coupled relation against the bias of spring 27. When the generator 22 has cooled to the aforementioned point, i.e., to the point where its output is below the drop-out level, the spring 27 returns the parts to the position shown in FIGURE 1 to complete a cycle of operation in which the ratchet wheel 30 and driven gear 17 have been advanced one step. As long as the member 28 is heated by the pilot burner 40, the device will continue to cycle in accordance with the heating and cooling of the thermoelectric generator 22 as it is alternately separated from and engaged with the member 28.

The time interval during which the electromagnet 19 is attracted is determined in great measure by the heat lag of the thermoelectric generator 22 used. However, one such time interval, shown by way of example only, is in the neighborhood of five seconds when the generator 22 used is of the type aforementioned as set forth in the copending application of Robert W. Fritts. In order to provide a factory adjustment of the time interval during which the electromagnet is attracted, and thereby of the period of oscillation of the lever 18, an adjustable resistance, shown schematically at 38, may be disposed in the thermoelectric circuit such as in connector 24. By varying the resistance characteristics of the thermoelectric circuit, the time interval of cooling the generator to the predetermined drop-out current level may be adjustably varied as desired.

It is to be particularly noted that there may be reversal of parts as desired particularly in that the electromagnet 18 may be fixed and the armature 26 may be movable with the rocker lever arm 18. Also the heat source 36 may take any suitable or desired form other than that shown and may be movable with respect to the thermoelectric generator 22 which may be fixed.

It is to be particularly noted that since the instant device is dealing with thermoelectric power, it is dealing with electrical energy measured in terms of milliwatts. The instant device which has no contacts in this thermoelectric circuitry therefore affords essentially trouble free operation.

Although a specific embodiment of the invention has been shown and described, it is with full awareness that many modifications thereof are possible. The invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the appended claims. What is claimed by the invention is:

1. In combination, a driven member, means affording substantially constant speed step-by-step actuation of said driven member comprising oscillatable electro-responsive operator means, ratchet means driven by said operator means and drivingly associated with said driven member to move the latter at a predetermined speed, and energizing means, said energizing means comprising a source of heat energy, and a heat responsive electric energy source means having a heat sensing portion, at least one of said heat source means and said sensing portion being oscillatable with respect to the other between heating and cooling positions, biasing means biasing said at least one of said heat sensing portion and source means toward said heat ing position, said electric energy source means being connected in circuit with said operator means for normally energizing the latter in response to disposition of said heat source and heat sensing portion in said heating position for a predetermined time interval, oscillatable lever means affording a connection between said oscillatable operator means and said ratchet means, and between said operator means and the oscillatable one of said heat source and heat sensing portions to effect, upon energization of said operator means, actuation of said driven member and simultaneous disposittion of said heat source and heat sensing portion in said cooling position, cooling of said heat sensing portion for a predetermined time interval etfectin g deenergization of said operator means to cause return of the oscillatable one of said heat source and heat sensing portion to said heating position under its bias, and means affording an adjustment of the electrical characteristics of said circuit to vary said predetermined heating and cooling intervals and thereby the period of oscillation of said lever means and hence the speed of said driven member.

2. In combination, a driven member, means for driving said driven member comprising an electroresponsive operator having an oscillatable member oscillatable between deenergized and energized positions and energizing means for said operator including a source of heat energy and heat responsive electric energy source means having a heat sensing portion relatively movable with respect to said heat source between first and second positions, said electric energy source means being connected in circuit with said operator for energizing the latter when said heat sensing portion is in said first position, means affording an actuating connection between said oscillatable operator member and said driven member and also between said member and said energizing means for causing actuation of said driven member and relative movement of said sensing portion and said heat source from said first to said second position on movement of said oscillatable operator member to energized position, and for causing return of said sensing portion and said heat source to said first position upon movement of said operator member to deenergized position, and means for selectively varying the period of oscillation of said operator member and thereby the rate at which said driven member is actuated.

3. In combination, a driven member, means for driving said driven member comprising an electroresponsive operator operable when energized to afford actuation of said driven member, energizing means. for said operator including a source of heat energy and a thermoelectric generator having a heat sensing thermojunction relatively movable with respect to said heat source between first and second positions, said generator being connected in circuit with said operator for energizing the latter when said thermojunction is in said first position, and lever means including a pivotally mounted member having means biasing the same in one direction and aflording an electrical and mechanical connection between said operator and said energizing means, said operator when energized tending to pivot said member in another direction to thereby cause relative movement of said thermojunction and said heat source from said first toward said second position, said biasing means on deenergization of said operator tending to cause pivoting of said member in said one direction and thereby relative movement of said thermojunction and said heat source from said second being connected in circuit with said operator means for normally energizing the latter when said heat source and thermojunction are in said heating position, and oscillatable lever means affording a connection between said oscillatable operator portion and said ratchet means and between said operator portion and the oscillatable one of said heat source and thermojunction to effect, upon energization of said operator means and movement of the oscillatable portion thereof to energized position, actuation of said driven member and simultaneous disposition of said heat source and thermojunction in said cooling position, said lever means also efiecting return of the oscillatable one of said heat source and thermojunction to said heating position upon movement of said oscillatable operator portion to deenergized position in response to deenergization of said operator means caused by cooling of said thermojunction.

5. In combination, a driven member, means affording step-by-step actuation of said driven member comprising oscillatable electroresponsive operator means having a portion oscillatable between energized and deenergized positions, ratchet means operatively associated with said operator means and drivingly associated with said driven member to move the latter at a predetermined speed, and energizing means for said operator means, said energizing means comprising a source of heat energy, and a thermoelectric generator having a heat sensing thermojunction, one of said heat source and thermojunction being oscillatable with respect to the other between heating and cooling positions, means biasing said oscillatable one of said heat source and thermojunction portions toward said heating position, said generator being connected in circuit with said operator means for normally energizing the latter when said heat source and thermojunction are in said heating position, and oscillatable lever means affording a connection between said oscillatable operator means and said ratchet means, and between said operator means and the oscillatable one of said heat source and thermojunction to efiect, upon energization of said operator means and movement of the oscillatable portion thereof to energized position, actuation of said driven member and simultaneous disposition of said heat source and thermojunction in said cooling position, said biasing means acting through said lever means upon deenergization of said operator means caused by cooling of said thermojunction to eifect return of the oscillatable one of said heat source and thermojunction to said heating position and movement of said oscillatable operator portion to deenergized position.

References Cited inthe file of this patent UNITED STATES PATENTS 658,997 Perret Oct. 2, 1900 2,097,838 Karrer Nov. 2, 1937 2,385,530 Paille Sept. 25, 1945 2,710,371 Baensch June 7, 1955 2,919,358 Marrison Dec. 29, 1959 FOREIGN PATENTS 239,503 Great Britain Apr. 15, 1926 199,906 Germany July 4, 1908 199,907 Germany July 4, 1908 

